I am going to go back here to a previous thread almost a year ago. Since this current thread- as has happened in the past- had many links posted that did not show evidence in favor of vitamin D for PC and even showed a so called U shaped curve where more than just a little D was actually harmful, I feel as though this study is needed for balance. Though the purpose of the OP was just to bring up a very strong result/RCT re: vitamin D in cancer in general, I feel the purpose got side tracked in the usual debate/battle, so I will throw in a pretty good study(IMO) specifically for PC, though still not RCT. No older 2007 study on post menopausal women here, all PC and much newer(2014) so enjoy everyone! (or not)
This was put out by the folks at Departments of Cancer, Biology, Urology, and Epidemiology and Prevention, Wake Forest University School of Medicine, Winston-Salem, North Carolina. So, they don't sound like a suspicious group from big vitamin D who want to corner the Vit D market. They are probably a pretty reasonable bunch of scientists well aware of the scientific method. They examine the SELECT trial on selenium and Vit E, which often gets mentioned here showing how dangerous vitamins can be. But there was apparently also a Vitamin D arm, and it was pretty impressive, almost as impressive as the study in my OP. And these researchers seem to think a U shaped curve that was found(but only in white men) was due to a selection bias. They are including the Prostate Cancer Prevention Trial (PCPT) along with SELECT. I had always argued against the U shaped curve when I looked at one of those studies closely, and I saw a reverse U shape, where the middle range of blood D had the highest rates for lower risk PC, and then rates started dropping sharply as rates began increasing, and the blood levels were not all that high even at higher levels. Though I guess that was not the case here. But these guys seem to be saying that any U shaped curve was due to selection bias.
cebp.aacrjournals.org/content/23/8/1447.longSomebody said...
The effects of blood levels of 25-hydroxyvitamin D (25-OHD) on the risk of total, low-, and high-grade prostate cancer were examined in the Selenium and Vitamin E Cancer Prevention Trial (SELECT) and the Prostate Cancer Prevention Trial (PCPT). In the SELECT study, plasma 25-OHD levels were associated with a linear decrease in prostate cancer risk for high-grade cancers in African American men and an apparent “U”-shaped effect in other men. The “U-shaped” curve may reflect detection bias. In the PCPT study, in which detection bias was minimized, serum 25-OHD levels were associated with a linear decrease in the risk of high-grade prostate cancers. The results from these large prevention trials support the hypothesis that circulating levels of 25-OHD decrease the risk of clinically relevant prostate cancers. Cancer Epidemiol Biomarkers Prev; 23(8); 1447–9. ©2014 AACR. ............
So, in the high risk PC guys, a linear decrease with higher levels of Vitamin D. Well, turns out breast cancer in post menopausal women may not be the only thing Vitamin D may well be helpful for, after all! Who would have thought that since they are so totally unrelated? Not me!
More detail:
Somebody said...
The hypothesis that vitamin D, or its major source, sunlight, inhibits prostate cancer has gone from a “dark horse” to a front-runner in the race to understand the epidemiology of prostate cancer. Clinically relevant prostate cancer preferentially afflicts the elderly, Blacks, and residents in northern latitudes (1). Conversely, the prevalence of subclinical prostate cancer (cancer detected in asymptomatic men) increases with age but does not vary by race or geography..................................
Although the results of experimental studies of vitamin D and prostate cancer have been uniformly positive, the results of observational studies have been mixed.........................
Trial (SELECT), a randomized, placebo-controlled trial of selenium and vitamin E on prostate cancer risk (18). Data for this case–cohort analyses included 1,731 cases and 3,203 controls.......the risk of total prostate cancer for non-African American men was U-shaped..............
Conversely, among the 250 African American cases, the risk of high-grade prostate cancer decreased linearly with increasing levels of 25-OHD...............................
An important limitation of the SELECT study is that the use of PSA screening and prostate biopsy was not controlled...........If the anomalously high 25-OHD levels in older men resulted from recent vitamin D supplementation (which seems likely), then the (pre-supplementation) association between plasma 25-OHD and prostate cancer risk would be distorted upwards. ....................In a second study in this issue, Schenk and colleagues examined associations between serum 25-OHD and prostate cancer risk in a case–control trial nested with the Prostate Cancer Prevention Trial (PCPT), a double-blind placebo-controlled trial of finasteride for the primary prevention of prostate cancer (22). This study included 1,695 men with prostate cancer and 1,682 controls. An important advantage of the PCPT study was its ability to minimize detection bias. All men had annual PSA and digital rectal examinations and the absence or presence of prostate cancer was confirmed by biopsy either during (for cases) or at the end of the trial (for all men). The key finding was that among combined treatment arms of this trial, comparing the highest with lowest quartile of serum 25-OHD, 25-OHD levels were associated with a linear decrease in the risk of Gleason 8–10 prostate cancer [OR, 0.55; 95% confidence interval (CI), 0.32–0.94]. There was no evidence of a preventive effect for Gleason 2–6 cancers, which were nonsignificantly increased, or of a “U”-shaped curve.
What is the “take-home” message from these studies? First, both studies support a protective role for circulating 25-OHD on prostate cancer risk. The effect was clearer in the PCPT study, which found that 25-OHD levels were associated with a linear decrease in risk of Gleason 8–10 prostate cancer, than in the SELECT study, which found that 25-OHD was associated with a linear decrease in the risk of high-grade cancers in African Americans and an apparent “U”-shaped curve in other men. Because a “U”-shaped curve was observed in the SELECT study, which was vulnerable to detection bias, but was not observed in the PCPT study, which was largely free from this bias, the “U”-shaped curve in the SELECT study may reflect such bias.
Second, both studies show that the protective effect of 25-OHD was associated more strongly with high-grade than with low-grade prostate cancers. This finding is consistent with the hypothesis that vitamin D inhibits the development of clinically relevant, but not subclinical prostate cancer (2). To return to our automotive example, seat belts prevent serious injury and death from automobile collisions; they do not prevent whiplash, a common but non–life-threatening injury (23). Thus, if fatal and nonfatal automobile injuries were combined into the single category, “injuries,” the life-saving effect of seat belts could be missed. This may be relevant to some of the inconsistency in previous reports of circulating 25-OHD and risk of (predominantly low grade) prostate cancer.
These seem like pretty strong results, even if not RCT quality. But enough for me to keep them in mind when deciding if I will, or will not, monitor my vitamin D levels. It is very consistent with my study in the OP regarding other cancers in women, which was an RCT. This study seems pretty reassuring about
using reasonable amounts of Vit D(with blood testing) where we need it most, high risk PCs, and seems to refute/rebut any U curve claims. It is a reassuring study until we finally get- as we wait an eternity- for those RCTs. Comments?
Post Edited (BillyBob@388) : 2/3/2016 7:06:24 AM (GMT-7)